gulp 3在sass之后运行rtl时给出了excptionn

Question

运行默认任务(sequence of 3 tasks sass then RTL then minify )时，gulp会抛出异常，并抛出此错误Unknown word

我将gulp 3与gulp-sass，gulp-RTL，gulp-uglify一起使用 运行默认任务时，出现异常并尝试了很多事情，但没有结果

//这里例外

de_modules\postcss\lib\lazy-result.js:248
        if (this.error) throw this.error;
                        ^
CssSyntaxError: <css input>:4363:3: Unknown word
    at Input.error (..\node_modules\postcss\lib\input.js:119:22)
    at Parser.unknownWord (..\node_modules\postcss\lib\parser.js:506:26)
    at Parser.other (..\node_modules\postcss\lib\parser.js:171:18)
    at Parser.parse (..\node_modules\postcss\lib\parser.js:84:26)
    at parse (..\node_modules\postcss\lib\parse.js:24:16)
    at new LazyResult (..\node_modules\postcss\lib\lazy-result.js:70:24)
    at Processor.process (..\node_modules\postcss\lib\processor.js:117:12)
    at DestroyableTransform._transform (..\node_modules\gulp-rtlcss\index.js:26:47)
    at DestroyableTransform.Transform._read (..\node_modules\readable-stream\lib\_stream_transform.js:184:10)
    at DestroyableTransform.Transform._write (..\node_modules\readable-stream\lib\_stream_transform.js:172:83)

//exception ends here    


// sass compile
    var gulp = require('gulp');
    var sass = require('gulp-sass');
    var minifyCss = require("gulp-minify-css");
    var uglify = require("gulp-uglify");
    var rtlcss = require("gulp-rtlcss");
    var runSeq = require('run-sequence');
    var gulpIf = require('gulp-if');

    gulp.task('sass_plugins', function () {
        var tasks = [];
        tasks.push(sass_plugins());
        return tasks;
    });

    gulp.task('minify_plugins', function () {
        // minify 
        var tasks = [];
        tasks.push(minify_plugins());
        return tasks;
    });

    gulp.task('rtl_plugins', function () {
        var tasks = [];
        tasks.push(rtl_plugins());
        return tasks;
    });

    var sass_plugins = function () {
        var tasks = [];
        // bootstrap compilation
        tasks.push(
            gulp
            .src('./assets/src/sass/bootstrap.scss')
            .pipe(sass())
            .pipe(gulp.dest('./assets/dist/global/plugins/bootstrap/css'))
            );
        // select2 compilation using bootstrap variables
        tasks.push(gulp
            .src('./assets/plugins/select2/sass/select2-bootstrap.min.scss')
            .pipe(sass({ outputStyle: 'compressed' }))
            .pipe(gulp.dest('./assets/dist/global/plugins/select2/css'))
            );
        return tasks;
    };

    var minify_plugins = function () {
        // css minify plugins
        var tasks = [];
        tasks.push(gulp
            .src(['./assets/dist/global/plugins/bootstrap/css/*.css', '!./assets/dist/global/plugins/bootstrap/css/*.min.css'])
            .pipe(minifyCss())
            .pipe(rename({ suffix: '.min' }))
            .pipe(gulp.dest('./assets/dist/global/plugins/bootstrap/css')));
        tasks.push(gulp
            .src(['./assets/dist/global/plugins/select2/css/*.css', '!./assets/dist/global/plugins/select2/css/*.min.css'])
            .pipe(minifyCss())
            .pipe(rename({ suffix: '.min' }))
            .pipe(gulp.dest('./assets/dist/global/plugins/select2/css')));
        return tasks;
    };
    gulp.task('default', function (cb) {
        runSeq('sass_plugins', 'rtl_plugins', 'minify_plugins', cb);
    });

我想让默认任务运行这3个任务，请帮助 当分别运行每个任务时，它运行良好